1. Field of the Invention
In the vast majority of cases, the fill level of liquids, e.g. fuel in a vehicle fuel tank, is still recorded using mechanical systems. In view of the increasingly widespread use of contactless signal acquisition systems, it would seem desirable to replace mechanical fill level recording systems with a contactless signal acquisition method not requiring physical contact.
2. Description of the Prior Art
Current devices for recording fill level generally utilize mechanical signal acquisition systems that function in cooperation with a potentiometer. In such cases, the potentiometer is disposed in the bottom area of a container that is intended to accommodate a liquid. However, the bottom of these containers is also where the lubricants and particles in the liquid collect and so come into direct contact with the potentiometer. As a result, particles may be deposited on the potentiometer, which is thus susceptible to corrosion and may suffer the effects of wear.
Particles that are deposited on the bottom of the vehicle""s fuel tank are swirled as a result of the driving motion of the vehicle, but new particles or suspended particles and sources of abrasion may infiltrate the tank at each refueling, depending on the purity of the fuel, and may impair the functioning of the potentiometer, particularly the accuracy with which a slider contacts a coil that is normally conformed on the potentiometer.
In the case of stationary containers, deposited particles are not swirled because the driving motion that occurs with vehicles is absent, with the result that contaminants may build up quickly and have a corrosive effect on the potentiometer.
With the solution suggested according to the invention, the resiliency of contactless recording is increased significantly for the same effort in terms of signal acquisition. Since the principal of signal acquisition remains the same, the connection of the device suggested according to the invention does not entail substantial modification of the downstream analysis system. Additional effort that might be required in terms of electronic equipment if, for instance, a Hall probe or an optoelectronic analysis system were used, may therefore be disregarded. Moreover, the effort in respect of peripheral cleanliness is substantially reduced when a flexible contact element according to the suggested solution is used, which particularly favors use of such a contact element even in environments that present threats of heavy soiling and particles.
The motion device that is usedxe2x80x94for examplexe2x80x94in recording the level of fuel in a fuel tank may be retained in large part and does not need to be fundamentally modified. A flexible contact element in the form of a rod is used and may take the place of a slider that cooperates with a potentiometer. A magnetic head is arranged at one end of the rod-shaped, flexible contact element and is movable relative thereto. The float and the lever from known recording motion devices may be used in most cases. The motion is only transferred to a magnet, which may be used as a recording element, or to a pressure element. Depending on the method, the motion may be transferred magnetically or via a pressure element acting on a resistor track.
A particularly simple and elegant embodiment is achieved if the flexible contact element is mounted vertically inside a tube that may be accommodated in a container or may project thereinto. A magnetic element furnished with a float is movable relative to the flexible contact element according to the level of liquid in the tube. A coating of ferromagnetic material applied to the wall of the flexible contact element is brought into contact with a resistive coating that is applied to the inside wall of the flexible contact element opposite the ferromagnetic material by the magnet, thus creating a short circuit between the resistive coating and the ferromagnetic coating. The electrical signal produced in this manner may be measured for example at the ends of the flexible contact element.
The electrical signal reflects the liquid level of, for example, fuel in a vehicle""s fuel tank.
When the fill level detection system according to the invention is used in stationary containers and in mobile containers, e.g. fuel tanks, brake fluid reservoirs, receptacles for windshield washer liquid or hydraulic fluid, other motion devices may be used instead of floats and may move the magnet or permanent magnet that replaces the slider relative to the flexible contact elementxe2x80x94e.g. of a rubber hose containing one resistive and one ferromagnetic coatingxe2x80x94that replaces the corresponding slider track. It is also possible to arrange the permanent magnet on an articulated rod, a toggle link or the like. If a magnet is arranged on such a motive system, it is also possible to create relative movement between the magnet and the flexible contact element.
In the case of horizontally disposed flexible contact elements, the float movement may be articulated to provide radial motion about a pivot point for example via a perpendicularly conformed lever arm. This causes the end of the rod that is furnished with a magnetic acquisition head to move radially along the contact hose. The distance of this movement is defined by the length of the rod to the pivot point. A horizontal hose alignment may also be selected instead of a radial hose alignment, in which case the only difference would lie in the proportion of the distances.